Process for the production of boronnitrogen compounds



- z 994 698 PROCESS FOR THE iRODUCIION F BORON- NITROGEN COMPOUNDS Friedrich Schubert and Konrad Lang, Leverimsen, Germany, assignors to Farbenfabrilren Bayer Aktlengesell- 5 Leverltuen, Germany, a corporation oi Ger- No Drawing. Filed Apr. 1, 1959, Ser. No. 803,353 Claims priority, application Germany Apr. 5, 1958 11 Claims. (Cl. 260-290) a The present invention relates to an improved and efiicient process of producing boron-nitrogen compounds. Copending application Ser. No. 761,667 which was filed on September 18, 1958, in the name of Konrad Lang,

Friedrich Schubert and Dieter Goerrig, describes a proc- 15 ess f0r.the production of boron-nitrogen compounds whichvmay carry organic substituents on the nitrogen atom, by contacting ammonium salts, which may be organically substituted on-the' nitrogen atom, and alkali metal or alkaline-earth metal boranates in the presence of liquid ammonia or liquid amines and filtering ofi the precipitated alkali metal or alkaline-earth metal salts. This reaction produces first a possibly organically substituted ammonium boranate ([R,NH] BIL) which splits 03 hydrogen so that borazane (R,N.BH,) is obtained:

( s n F s s'is wherein R is H, an aromatic or aliphatic radical and X is an acid radical.

In the process described in said copending application Ser. No. 761,667 borazanes (R;N.BH,) are obtained by reacting alkali metal or alkaline-earth metal boranates with ammonium salts, which may be organically substituted mmmx and amine am it the amine R5)! 5 is more volatile than R;'N and/or if the borazane R,N.BH; is thermally less stable than R,'N.BH,:

According to copending application Ser. No. 787,838 which was filed January 20, 1959, in the name of Eberhard Zirngiebl and Alex Burger, and which spplication is assigned to the assignee 'otthef present'spplicatiom'metal complex'boramites metalze'ompounds wherein the metal is comb ed in complex form, I-.-

or metal compounds which are dissolved in a complexforming solvent, with alkali metal or alkaline-earth metal boranstes. Boranates'ot cationic complexly bound heavy metals are obtained. Complexly bound boranstes ot e.g., 5

zinc, cadmium, chromium, mangsnesmeobalt' and nicltel are obtainable in this manner. These complex metal boranates are excellent starting materials for the production of borazanes.

In accordance with the present invention it has been According to s preferred embodiment of the invention, the metal combined in complex form is converted into a compound which is less soluble than the metal complest borsnate mIBsNBIBHs-i- QL'I'I I Patented Aug. 1, 1961 wherein m is the valency of the central atom; n is the co ordination number of the central atom; Me is the central atom, R is H, an aliphatic or aromatic radical; Lig is the complex ligand; X is an acid radical.

In the second reaction phase the ammonium boranate is converted into the borazane by splitting off hydrogen:

To ensure that the reactions proceed in the desire direction and so as to give optimum yields, definite conditions have to be chosen:

(1) Choice of the solvent (R N) It is of advantage to choose as solvent the amine which is the amine component of the borazane to. be produced. According to Equation 4 the ammonium boranatederived from the solvent is formed in the primary step or the reaction. If. the amine acting as a ligand (lig.) is more strongly basic than the solvent, a second boranate [Lig. H]BH is formed in a concurrent reaction. Another observation disclosed in said copending application Ser. No. 761,667, ishowever of essentially greater importance for the further course of the reaction; i.e. that .type .of borazane will be formed, the amine component of which is the least volatile of the possible amines which can be used or which is most stable among the possible borazanes which can be formed. Iiit is desired, however, to produce very stable-borazanes, which are fast to water wherein they are insoluble or substantially insoluhis (in this case, the amine combined in the complexlasa ligand component), water can be used as solvent or suspending agent respectively.

(2) Choice of the precipitant (HX) The system represented by the Equations4-and 5 is displaced by some operations in the direction of the borazane formation. lnEquation 4, the formation of the metal :salt (MeX which is very sparingly solublejn the solvent used and the elimination 0mm amine bonded as a ligand'fflig.) from the reaction mixture promote .the formation of the desired-ammonium boranate. In Equation 5, the splitting of! of hydrogen effects displacement of equilibrium. I

As a result of the slightsolubility of the complex bdrfanates" inthe" solvents to be 'use'd and thefstability oi the complexesythe number ot-free metal ions in the-solution is low. The desired displacement of equilibrium can be accomplished byadoptingf two'methods; (a) precipitation of anextremely sparingly soluble memos; especially suitable an this purpose are the 'sulfide'a'felg. H 8 o'r solu- 0 tions arms-mine amines (R';N) as"a prccipita'ntfand (b) the decomposition .ot .tl 1e complex boranate by removins e iz s. l.s-. onv n ,i t amman sw 4 or into free CO, or carbonates, it carbonato 'com'plbiriis are used or into organic derivatives if amine complexes are used.

In order to obtain optimum results it is of advantage to use precipitants having only a moderate acidity, i.e. precipitants which do not attack the MI,- or BIL-grouping and moreover do not have an oxidizing action on these so two groups and do not lead to the formation of water which is relevant when operating in an anhydrous system. A precipitant combining all these properties is H 8. Be-

' 'sides, most ammonium sulfides are unstable compounds so that excess H,S canotten be removed from the amine solutions very easily by distillation.

(3) Choice of the ligand (lig.) The properties of the complex ligands to be used in the process of the invention may vary within wide limits;

care has to be taken only, as is set forth in said copending application Ser. No. 761,667 in respect of volatility and borazane stability.

When observing the aforesaid conditions extraordinarily good yields of borazane are obtained. As described in the example below, the yields are in most cases 100% of the theoretical or only slightly lower. Such high yields could hitherto not be obtained by other processes. Another advantage brought about by the herein described process resides in the fact that also very sensitive borazanes the amine component of which is e.g. a primary or secondary amine and which tend to split off hydrogen, can be obtained in a yield of 100%. These phenomena are in particu ar due to the very mild reaction cor .iitions. Besides, the process of the invention allows of producing substantially all borazanes by the use of ordinary laboratory devices as well as technical apparates.

In the following example general instructions are given for the production of boron-nitrogen compounds.

Example.ln a three-necked flask equipped with a reflux condenser a stirrer and a gas inlet pipe, a metal amine boranate is suspended in an organic amine in such a quantity so as to form a thin suspension which can easily be stirred. Hydrogen sulfide (purified by means of a Na s solution and dried over Cacl is passed into the suspension until a sample of the precipitate does not evolve hydrogen any longer after addition of an acid. The suspension is then filtered and the excess amine is removed from the filtrate by distillation. The borazane can if desired be further purified by distillation or dissolving in ether, shaking with charcoal and evaporation. Because of the ready volatility of the (C11,),NH, the prodnction of N-dimethylborazane is preferably accomplished by shaking the reaction mixture twice with ether, purifying it with active carbon and evaporation. Pure borazane is thus obtained.

Borazane is obtained e.g. in the following yields:

Complex boranate or solvent reap.

What we claim is: 1. Process for preparing (C,H ),N.BH,, which comprises treating [Cd(NH,).].(BH suspended in with hydrogen sulfide and recovering (C,H,),N.BH,.

2. Process for preparing (CI-LhNI-LBH; which comprises treating [Cd(NH,).] (8H suspended in ah with hydrogen sulfide and recovering (Cl-LhNHBH,

R;N, defined as above, as solvent, and recovering the kyl amines.

5o fide'is hydrogen sulfide.

4. Process -for preparing (C H N.BH which comprises treating [Zn(NH (EH suspended in with hydrogen sulfide and recovering (C,H N.BH 5. Process for preparing (C,H N.BH which com-f prises treating [Cd(CH NH,) (EH suspended in with hydrogen sulfide and recovering (C H N.BH

6. A process for preparing amine boranes having the general formula R NBH wherein R N represent a ni-i trogen containing compound selected from the group consisting of secondary and tertiary lower alkyl amines,i pyridine and ammonia which comprises reacting a boro-f hydride of a cationic complexly bound heavy metal se-, lected from the group consisting of zinc, cadmium, man-i ganese and nickel having a complex coordinate linkingradical between the borohydride anion and heavy metal:

cation with a sulfide in a liquid nitrogen-containing base amine borane thereby formed.

7. A process according to claim 6 in which said liquid nitrogen-containing base is a member selected from the group consisting of secondary and tertiary lower al- 8. A process according to claim 7, in which said alkyl amine is (0H,),NH.

9. A process according to claim 6, in which said liquid nitrogen-containing base is ammonia.

10. A process according to claim 6, in which said liquid nitrogen-containing base is pyridine.

11. A process according to claim 6, in which said sul- References Cited in the file of this patent UNITED STATES PATENTS Chamberlain et a1. Aug. 4, 1959 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No; 2,994,698 August l 1961 Friedrich Schubert et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 57, strike out "boranates line 63,

strike out "boranate".

Signed and sealed this 17th day of April 1962,

(SEAL) Attestz' ESTON 3 JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

6. A PROCESS FOR PREPARING AMINE BORANES HAVING THE GENERAL FORMULA R3N.BH3 WHEREIN R3N REPRESENT A NITROGEN CONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF SECONDARY AND TERTIARY LOWER ALKYL AMINES, PYRIDINE AND AMMONIA WHICH COMPRISES REACTING A BOROHYDRIDE OF A CATIONIC COMPLETELY BOUND HEAVY METAL SELECTED FROM THE GROUP CONSISTING OF ZINC, CADMIUM, MANGANESE AND NICKEL HAVING A COMPLEX COORDINATE LINKING RADICAL BETWEEN THE BOROHYDRIDE ANION AND HEAVY METAL CATION WITH A SULFIDE IN A LIQUID NITROGEN-CONTAINING BASE R3N, DEFINED AS ABOVE, AS SOLVENT, AND RECOVERING THE AMINE BORANE THEREBY FORMED. 